Opposing ethanol self-administration behaviors are observed when comparing two strains of mice: C57BL/6J x NZB/B1NJ F1 hybrids (B6xNZB) avoid ethanol (avoiders) after experience with high concentrations of eth- anol and C57BL/6J x FVB/NJ F1 hybrids (BGxFVB) do not (revelers). The overarching hypothesis of this proposal is that these hybrids differ in sensitivity to the aversive, but not rewarding or anxiolytic, properties of ethanol and differential levels of FosB and AFosB in specific cell types and brain regions reflects experience dependent differences in voluntary ethanol self-administration. Hybrid sensitivity to aversive, rewarding, and anxiolytic properties of ethanol will be determined by employing the following tests; conditioned taste aver- sion, conditioned place preference, modified two bottle choice, and elevated plus maze. To define neuro- circuits engaged by ethanol avoidance and revelry, FosB and AFosB immunoreactivity will be measured in ethanol experienced hybrids. Neuronal cell types of FosB and AFosB expressing neurons will also be deter- mined. Effects of strain, dose, and quantity of FosB/AFosB positive nuclei (per brain region and cell type) will be determined. These experiments will contribute to the understanding of alcohol use and abuse.